Apparatus for computing flow rate of thermoplastic material

Abstract

Disclosed is a method and device for automatically and instantaneously computing and displaying with high precision the flow rate of thermoplastic samples run in an extrusion plastometer in accordance with American Society of Testing Materials (ASTM) Method D1238. The method and device comprise using a microcomputer and related circuitry to monitor and control the measurement process and subsequently compute the resulting flow rate.

We claim: 
     
       1. In a device for determining the flow rate of a thermoplastic material in accord with Procedure B of ASTM Method D1238 using an extrusion plastometer, the improvement comprising means for entering one or more numerical factors specified by said ASTM Method D1238 for said thermoplastic material into an input/output device capable of being read by a microprocessor,   means for initiating an electronically timed interval when a change of state is detected in a switch designed to undergo a first change of state after displacement of said thermoplastic material begins in said plastometer,   means for checking the status of said switch at predetermined intervals,   means for ending said electronically timed interval when said switch undergoes a second change of state upon the displacement of a predetermined volume of said thermoplastic material,   means for determining the duration of said timed interval,   means for calculating the flow rate for said thermoplastic material by dividing said factor by the duration of said timed interval, and   means for displaying said flow rate in a convenient input/output device.   
     
     
       2. The device of claim 1 wherein said means for entering said numerical factors is a set of thumbwheel switches. 
     
     
       3. The device of claim 1 wherein said means for displaying said flow rate is a set of LED displays. 
     
     
       4. The device of claim 3 wherein said means for entering said numerical factors is a set of thumbwheel switches. 
     
     
       5. The device of claim 1 wherein said means for entering said numerical factors is a keyboard. 
     
     
       6. The device of claim 1 wherein said means for displaying said flow-rate is a printer. 
     
     
       7. The device of claim 1 wherein a preheat timer is initiated prior to the start of the extrusion of said thermoplastic material.